Open-Shell Pd(II) and Ni(II) Complexes Supported by Cyclic(alkyl)(amino)carbene-Derived Carbon Disulfide Radical Ligands.

Radical ligands play a crucial role in modifying the electronic structures and reactivity of transition-metal complexes, often endowing them with unique properties. In this study, we demonstrate that a cyclic-(alkyl)-(amino)-carbene (CAAC)-derived carbon disulfide adduct functions as a radical ligand, supporting Pd-(II) and Ni-(II) complexes with multiconfigurational electronic structures. Single-crystal X-ray crystallography confirms that both 1-Pd and 1-Ni adopt a square planar geometry with structural parameters consistent with the presence of ligand-centered unpaired electrons. Computational studies indicate that both complexes favor an open-shell singlet ground state, with small energy gaps to the triplet and closed-shell singlet states, which could likely facilitate electronic state mixing. This work highlights the effectiveness of CAAC-derived radical ligands in stabilizing multiconfigurational electronic states in metal complexes, opening avenues for potential applications in catalysis and materials science.